AmoxycillinInfections caused by bacteria that are sensitive to amoxycillin. Amoxycillin is a commonly used penicillin that works against a wide range of bacteria. It is in the group called beta-lactams. Amoxycillin (and the others in the beta-lactam group) works by stopping the making of the cell wall of susceptible bacteria, causing the bacteria to die. Some bacteria are not susceptible to amoxycillin, but they might be susceptible to other penicillins, or other antibacterials. Your doctor will sometimes swab the area of infection to see which is the best antibacterial to give.